This invention relates to a sealing system for sealing a rotating shaft against leakage of gas/liquid mixtures such as air/oil mixtures contained in lubricating oil sprays in crankcases of internal combustion engines. The shaft seal system is of the type which has a revolving lip seal ring whose sealing lip, preferably under the effect of centrifugal forces, lifts off the shaft during revolution and a labyrinth sealing ring arranged on the gas/liquid side, adjacent the lip seal ring.
Elastomer lip seal rings are effectively used as shaft seal rings for sealing against leakage of liquids or gases which may be under different pressures. In case, however, gas/liquid mixtures such as air/oil mixtures are to be sealed, for example, in diesel engines, the dust and dirt particles entrained with the oil may deposit on the sealing lip and may cause damages and an eventual leakage of the fluid to be sealed. In particular, particles entrained by lubricating oil sprays may rapidly cause damages to the sealing lip, thus resulting in leakages, particularly where the crankshaft ends pass through the crankcase of a high-performance diesel engine in which the lubricating oil has a higher proportion of solid particles or the lubricating oil has a higher viscosity due to the combustion process. On the average, present-day crankshaft seals in diesel engines become inoperative frequently after a relatively short running period.
U.S. Pat. No. 3,459,431 discloses an elastomer lip seal ring for use in an oil-filled bearing. The lip seal ring has an axial elastomer projection at the air side protected by a metal ring which is bent approximately in a U-shaped manner over the projection without contacting the same and which rotates with the shaft. During operation, in the gap between the ring and the projection, dust, dirt, and vapor are deposited and thus the sealing lip proper is protected from damages or destruction. For crankshaft seals, however, such protective measures cannot be taken because the air/oil mixture forming a fluctuating oil spray would pass through the gap and the sealing lip and the dust and dirt particles collected in the gap would be entrained and carried to the sealing lips where they would cause damage.
In published European Patent Application No. 117,267, a shaft sealing system for drives lubricated by oil mist is disclosed. The sealing ring system comprises a rotary elastomer lip seal ring and an oil filter ring mounted on the oil mist side adjacent the lip seal ring. The sealing lip functions as a stationary shield only at standstill or at low rpm's while at higher rpm's the sealing lip lifts off the shaft due to centrifugal forces. In the oil filter ring itself at higher rpm's oil droplets are separated from the oil mist under the centrifugal forces and the oil droplets are guided back to the drive by means of radial channels provided in the housing. The sealing lip proper remains free from oil deposits and is thus protected against damages or destruction.
Such systems, however, are not adapted for sealing crankshaft ends in crankcases. Particularly in case of substantial impurities, such as oil carbon which results from the combustion in diesel engines and which finds its way into the crankcase, the fluctuating lubricating oil spray in the crankcase clogs the oil filter with the dirt particles in a short time or fine dirt particles are not filtered out of the lubricating oil at all. As a result, the oil filter becomes inoperative and the lubricating oil which contains the dirt particles could eventually find its way through the channels to the sealing lip, causing damages and leakages by deposits.